Composition for electric insulators and method of preparing same



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' Pat ented Dec. 29, 1 925.

No Drawing.

UNITED STATES ABMAND L. LAIBBE, OF MURRAY, UTAH,

PATIENT OFFICE.-

ASSIGNOR TO AMERICAN SMELTING AND REFINING COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

COMPOSITION FOR ELECTRIC INSULATORS AND METHOD OF PREPARING SAME.

and useful Improvements in Composition for Electric Insulators and Methods of 4 Preparing Same, of which the following is a specification.

The invention relates in general to an improved insulator for a high tension electric current of the type which may be used to support the weight of some structure theresulators of the usual type and Where elecon and the invention also relates to anew composition of matter for use in forming electric insulators and to a method for forming such insulators.

While the insulator herein disclosed is of general application for use in any situation where it is desired to electrically separate two members having difi'erent electrical potentialities, the device illustrated .is particularly designed for use in situations where high voltage is used, where the presence of gases containin acid and moisture tend to interfere with t e efl'ective operation of introdes or other strain inducing parts are apt to crush the supporting insulators if they be made of frail construction.

As one illustration of a situation where the invention is particularly applicable, reference is made to an insulator exposed to the smoke or fumes passing from a metallurgical plant. In such cases it has been usual to mount the bars carrying the conductor on ordinary porcelain insulators.

These porcelain insulators have not proven satisfactory and break down after they have been in use for a while. It is believed that this is due to acids and moisture collecting on the surface which form a conductive coating. The current present passes through the coating thus formed, overheats the insulator and breaks the porcelain perhaps due to the unequal heating of the different parts of the same. Insulators made of other materials, such as marble have the objection that they are relatively expensive and also must be wiped off occasionally to remove accumulations but obviously this necessitates the interruption of the functioning of the apparatus in which they are mounted.

Accordingly, one of the objects of the Application filed August 16, 1921. semi No. 492,654.

over a relatively long period of time even under the deleterious conditions incidental to the passing of hot acid gases and moisture past the insulators.

Broadly, I attain this object of the invention by molding the insulators of a plastic composition which is formed entirely, or largely, of slack lime and in permitting the formed insulators to harden into any desired form.

As slackened lime is frangible and difficult to mold and handle, the invention also contemplates the uniting with the lime, of some 'body-forming-material together with a suitable binding material for uniting the substances into a body capable of maintaining its configuration even when subjected to disrupting strains. As an illustration of one such body substance reference is made to sand and Portland cement which is excellent as a binder. One composition which i has given entire satisfaction compris s slack lime 40 0 Portland cement 50 and sand 0 l I Wel it I n preparlng the material the lime which should be free of ma esia' is slacked for several days so as to msure against cracking of the formed block during the succeedmg drying operation.

The materials enumerated are forced through a forty mesh screen; mixed into a 99 soft paste and worked b hand into the molds'which are referab y made of iron. The composition is allowed to remain in the molds, covered with wet sacks, for several days, about three days being the usual time,

at the end of which period they are placed under water for a relatively long time, usually about ten days. At the termination of this water treatment the formed insulators are removed from the molds, dried at atmospheric temperature for about ten days,

after which they are subjected to a slow bakin operation usually for about ten days aT Fn of flat disks comprising a plurality of disks stacked one on the other to form a completed insulator.

The insulator herein disclosed has roven satisfactory in active operation and as an advanta e over other similar devices in that it readi y takes up both acids and condensed moisture from its environment, without impairing its dielectric efficiency. The lime present reacts with any sulphur-acid gases present to form calcium sulphate which is itself a good dielectric. The insulator disclosed has the further advantage in that it absorbs moisture at relatively low temperatures and liberates the same at the higher temperatures usually present in the g A still further advantage in the type of insulator herein disclosed is that after it has been punctured by the electric current passing therethrou h it can be slowly dried out for a period 0 about four days and at a temperature of about 160 F. after which treatment its dielectric strength is substantially re-established.

Having thus described my invention, I claim: c

1. A process of formin an electrical insulating material for hi voltage electric current which consists in mixing slacked lime substantially free from magnesia in the roportion of not less than 40% and Port and cement and sand in substantial proportions, said in edients being mixed to ether and forme into shape and then ba ed prior to use for insulating purposes. 2. A composition of matter for use as an electric insulating material comprising slacked lime, sand and Portland cement, and in the proportion approximately of lime, forty per cent, sand ten per cent and cement, fift per cent.

igned at Murray in the county of Salt Lake and State of Utah this ninth (9th) day of August A. D. 1921.

ARMAND L. LABBE. 

